1. Field of the Invention
The present invention relates generally to a method for cleaning the interior wall of tubes used in heat exchanger bundles, and more particularly to an improved method of cleaning the interior wall of a tube with a slurry and a tubular lance.
2. Description of the Prior Art
Heat exchanger tube bundles are used for the transfer of heat from a fluid media passing through a series of conduits or tubes. During this process, carbonaceous and calcareous deposits will form on the interior of the individual tubes and debris and other dirt will collect on the surface of the individual tubes. Therefore, in order to maintain efficient operation, it is necessary to periodically remove the tube bundles and clean the interior and exterior of the tubes.
One primary method of cleaning the interior of heat exchanger tubes includes the progressive insertion of a small diameter tube, known as a lance, having a nozzle with a plurality of jets at the leading end of the lance. As the nozzle-end of the lance is progressively inserted into the heat exchanger tube, a high pressure fluid, typically water, is pumped through the lance and the nozzle to clean the interior wall of the tube. The water pressure in the lance may easily exceed 10,000 pounds per square inch (psi) with flow rates in excess of 100 gallons per minute (gpm).
In many instances the carbonaceous and calcareous deposits are not easily removed by the above-described process and a single cleaning operation of the lance and high pressure water will not be adequate. Thus, it may be necessary to perform the cleaning operation several times to adequately remove stubborn deposits. Occasionally, the stubborn deposits are not removed after several attempts employing this process. Obviously, the efficiency and capability of cleaning several hundred tubes in a single heat exchanger bundle is greatly affected when it is necessary to perform multiple cleaning operations on individual tubes.
An alternative method of cleaning tubes having stubborn deposits is to dry sand blast the interior wall of the tube. Dry sand is blasted at the open end of the tube and is adequate for removing stubborn deposits near the end of the tube at which the sand enters the tube, but is inadequate along more distant sections of the tube due to the decreased velocity and impingement of the sand grains with the wall of the tube.
Accordingly, there exists a need for an improved method of cleaning the interior of tubes in a heat exchanger tube bundle in which a slurry can be propelled against the wall of the tube to remove stubborn deposits.